In a world of dwindling resources, waste is one thing in no danger of running out. Each Australian generates more than 2,000kg of waste per year, and around half of that ends up in landfill. But at least some of that waste could be turned into a resource that is both in demand and in decline: fuel.

The global waste-to-fuel industry is considering options as varied as agave, plastics and disused tyres to solve two environmental problems – reducing waste and increasing fuel production.

Landfill and agricultural wastes are already burned to generate heat and electricity, and methane is captured from landfill for the same purpose, but these technologies are both relatively low-hanging fruit.

“It is a new industry, so there are all the challenges associated with developing supply chains, building networks and developing technologies to convert products to fuels that meet quality standards and are cost-effective,” says O’Hara, also professor of biofuels and biorefining at Queensland University of Technology. “But fuel demand is growing in many industries and there is an opportunity to supply into that growing demand.”

There are three main categories of waste that have the potential to be converted to suitable fuels.

The first is crop wastes such as the fibrous sugar cane waste known as bagasse. Currently, bagasse is mostly burned to generate power, but it could be used to produce biofuel.

“The residues of existing crops offer a lot of opportunity because we’ve got very large-scale resources and the material is often already located at a facility which is operated maybe year-round,” O’Hara says.

Bagasse-based biofuel production could take place where the feedstock is found, which O’Hara says could be a significant contributor to regional and rural economies.

Recognising this, the Australian Renewable Energy Agency has just announced investment of $2.37m in an advanced biofuels laboratory being built near Gladstone in southern Queensland by Southern Oil Refining. The $16m pilot plant is scheduled to open next year and aims to transform bagasse and prickly acacia waste into one million litres of kerosene and diesel within three years.

One of these crops is agave – better known as the main ingredient in Mexican tequila. It’s a desert crop that can grow in low-rainfall conditions on land suitable for little else. University of Adelaide researchers have found it’s also energy-rich and could produce bioethanol at a rate that rivals existing bioethanol feedstocks such as sugar cane. And before tequila drinkers panic, this process would use the waste leaves of the plant, not the succulent core used to make the distilled liquor.

Waste tyres are one environmental eyesore that the federal government recently targeted with its tyre product stewardship scheme, which promotes “the development of viable markets for end-of-life tyres”.

Australian startup Green Distillation Technologies has developed the means to produce around 3,000 litres of oil from a single seven-tonne mining truck tyre. Its recycling process involves heating the tyre rubber in a low-oxygen environment, which produces a vapour that is condensed into oil.

Prof Richard Brown, director of the QUT Biofuel Engine Research Facility, says tyres have a significant energy advantage over agricultural waste.

“Sugar cane waste or wheat stubble or what’s left over after cropping might have 10-15 megajoules per kilogram,” Brown says. “Tyres are probably double that, they’re quite high and so it’s much easier to make them into something like a diesel or petrol fuel.”

Tyre oil does have slightly less embedded energy than conventional diesel, but it also seems to have a better emissions profile, producing less nitrogen oxide and fine particulates. A single tyre processing plant is expected to deal with around 685,000 tyres per year and produce 7,360 tonnes of oil from those tyres, as well as 7,000 tonnes of carbon and 2,000 tonnes of steel.

Another global environment issue is waste plastic. Plastic bottles, wrappers, film and containers are an eyesore that blights every inhabited corner of the world, but they’re also a valuable feedstock.

“Wherever there’s people, there’s this plastic problem,” says Bevan Dooley, chief executive of Integrated Green Energy. “By converting it to fuel, we stop more oil being taken out of the ground.”

Integrated Green Energy has developed a method of processing all forms of waste plastic, excluding Teflon and PVC, to produce petrol and diesel that meets Australian and international fuel standards. The process itself isn’t unique – it involves heating the plastic to 400C in a low-oxygen environment – but Dooley says the innovation is in making a pure product that can be used in any engine.

A single plant is capable of processing around 50 tonnes of plastic per day and producing 50,000 litres of petrol and diesel combined. The waste plastic feedstock needs to be shredded and washed, but the plant is at least partly powered by the liquid petroleum gas that is a byproduct of the process. Dooley says with GST and excise added, the fuel would retail for slightly less than regular diesel, but he stresses this is without relying on any kind of government subsidies.

Brown says biofuels could be a valuable supplement to the existing petroleum industry and contribute to diversification of energy supply, but would benefit from government incentives and policies to encourage the nascent industry on the road to economic sustainability.

“We’ve had a petroleum industry for about 100 years and they’ve got an infrastructure, oil refineries, tankers – the whole thing is all set up so they are doing good on a large scale and their cost per unit of production is very low,” he says. “Biofuel companies are doing small volumes, and they have high overheads so it’s much harder to penetrate into the market.”

Fount: https://www.theguardian.com/sustainable-business/2016/dec/16/transforming-waste-into-fuel-with-australian-innovations-from-tyres-to-sugar-cane-and-agave